Re: [Xen-devel] [PATCH for-4.6 4/4] xen/arm: Find automatically a PPI for the DOM0 event channel interrupt

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 12 Dec 2014, Julien Grall wrote:
> Use the new vgic interface to know which virtual PPI is free and use it
> for the event channel code.
> 
> At the DOM0 creation time, Xen still don't know which vIRQ will be free.
> All the vIRQ will be reserved when we parse the device tree. So allocate
> when the hypervisor node is created.
> 
> It's safe to defer the allocation because no vIRQ can be injected as
> long as the vCPU is not online.
> 
> Also correct the check in arch_domain_create to use is_hardware_domain.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> ---
>  xen/arch/arm/domain.c                | 13 ++++++++++---
>  xen/arch/arm/domain_build.c          | 10 ++++++++++
>  xen/arch/arm/platform.c              |  7 -------
>  xen/arch/arm/platforms/xgene-storm.c |  1 -
>  xen/include/asm-arm/platform.h       |  4 ----
>  5 files changed, 20 insertions(+), 15 deletions(-)
> 
> diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
> index 7221bc8..7d14377 100644
> --- a/xen/arch/arm/domain.c
> +++ b/xen/arch/arm/domain.c
> @@ -543,10 +543,17 @@ int arch_domain_create(struct domain *d, unsigned int 
> domcr_flags)
>      if ( (rc = domain_vtimer_init(d)) != 0 )
>          goto fail;
>  
> -    if ( d->domain_id )
> +    /*
> +     * The hardware domain will get a PPI later in
> +     * arch/arm/domain_build.c  depending on the
> +     * interrupt map of the hardware.
> +     */
> +    if ( !is_hardware_domain(d) )
> +    {
>          d->arch.evtchn_irq = GUEST_EVTCHN_PPI;
> -    else
> -        d->arch.evtchn_irq = platform_dom0_evtchn_ppi();
> +        /* At this stage vgic_reserve_virq should never fail */
> +        BUG_ON(vgic_reserve_virq(d, GUEST_EVTCHN_PPI));
> +    }

Why do we still need this, if we have another vgic_allocate_virq call in
make_hypervisor_node? Wouldn't that work for DomUs too?


>      /*
>       * Virtual UART is only used by linux early printk and decompress code.
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index c238c8f..8dedc60 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -625,6 +625,16 @@ static int make_hypervisor_node(struct domain *d,
>          return res;
>  
>      /*
> +     * The allocation of the event channel IRQ has been deferred until
> +     * now. At this time, all PPIs use by DOM0 has been registered
> +     */
> +    res = vgic_allocate_virq(d, 0);
> +    if ( res < 0 )
> +        return -FDT_ERR_XEN(ENOSPC);
> +
> +    d->arch.evtchn_irq = res;
> +
> +    /*
>       * interrupts is evtchn upcall:
>       *  - Active-low level-sensitive
>       *  - All cpus
> diff --git a/xen/arch/arm/platform.c b/xen/arch/arm/platform.c
> index cb4cda8..d016797 100644
> --- a/xen/arch/arm/platform.c
> +++ b/xen/arch/arm/platform.c
> @@ -160,13 +160,6 @@ bool_t platform_device_is_blacklisted(const struct 
> dt_device_node *node)
>      return dt_match_node(blacklist, node);
>  }
>  
> -unsigned int platform_dom0_evtchn_ppi(void)
> -{
> -    if ( platform && platform->dom0_evtchn_ppi )
> -        return platform->dom0_evtchn_ppi;
> -    return GUEST_EVTCHN_PPI;
> -}
> -
>  void platform_dom0_gnttab(paddr_t *start, paddr_t *size)
>  {
>      if ( platform && platform->dom0_gnttab_size )
> diff --git a/xen/arch/arm/platforms/xgene-storm.c 
> b/xen/arch/arm/platforms/xgene-storm.c
> index 416d42c..b0808b8 100644
> --- a/xen/arch/arm/platforms/xgene-storm.c
> +++ b/xen/arch/arm/platforms/xgene-storm.c
> @@ -232,7 +232,6 @@ PLATFORM_START(xgene_storm, "APM X-GENE STORM")
>      .quirks = xgene_storm_quirks,
>      .specific_mapping = xgene_storm_specific_mapping,
>  
> -    .dom0_evtchn_ppi = 24,
>      .dom0_gnttab_start = 0x1f800000,
>      .dom0_gnttab_size = 0x20000,
>  PLATFORM_END
> diff --git a/xen/include/asm-arm/platform.h b/xen/include/asm-arm/platform.h
> index eefaca6..4eba37b 100644
> --- a/xen/include/asm-arm/platform.h
> +++ b/xen/include/asm-arm/platform.h
> @@ -38,10 +38,6 @@ struct platform_desc {
>       */
>      const struct dt_device_match *blacklist_dev;
>      /*
> -     * The IRQ (PPI) to use to inject event channels to dom0.
> -     */
> -    unsigned int dom0_evtchn_ppi;
> -    /*
>       * The location of a region of physical address space which dom0
>       * can use for grant table mappings. If size is zero defaults to
>       * 0xb0000000-0xb0020000.
> -- 
> 2.1.3
> 

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